Modified pigments and process for preparing modified pigments

ABSTRACT

Processes for preparing modified pigments are described. In one embodiment, the process comprises the step of combining, in any order, a pigment having attached an electrophilic group and a thiol reagent comprising at least one —SH group and at least two ionic or ionizable groups. In a second embodiment, the process comprises the step of combining, in any order, a pigment having attached an electrophilic group and a thiopolymer comprising at least one —H group. Modified pigments are also described.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of prior U.S. patentapplication Ser. No. 10/142,596, filed on May 10, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to modified pigments and toprocesses for preparing modified pigments.

[0004] 2. Description of the Related Art

[0005] The surface of pigments contain a variety of different functionalgroups, and the types of groups present depend on the specific class ofpigment. Several methods have been developed for grafting materials and,in particular, polymers to the surface of these pigments. For example,it has been shown that polymers can be attached to carbon blackscontaining surface groups such as phenols and carboxyl groups. However,methods which rely on the inherent functionality of a pigment's surfacecannot be applied generally because not all pigments have the samespecific functional groups.

[0006] Methods for the preparation of modified pigment products havealso been developed which can provide a pigment with a variety ofdifferent attached functional groups. For example, U.S. Pat. No.5,851,280 discloses methods for the attachment of organic groups, suchas ionic or ionizable groups, onto pigments including, for example,attachment via a diazonium reaction wherein the organic group is part ofthe diazonium salt. The resulting surface-modified pigments can be usedin a variety of applications, such as inks, inkjet inks, coatings,toners, plastics, rubbers, and the like.

[0007] Other methods to prepare modified pigments have also beendescribed. For example, PCT Publication No. WO 01/51566 disclosesmethods of making a modified pigment by reacting a first chemical groupand a second chemical group to form a pigment having attached a thirdchemical group. Ink compositions containing these pigments are alsodescribed.

[0008] While these methods provide modified pigments having attachedgroups, there remains a need for improved modified pigments as well asfor processes for attaching groups and, in particular, polymeric groups,to a pigment. These additional methods may provide advantageous productsand alternatives for forming modified pigments.

SUMMARY OF THE INVENTION

[0009] The present invention relates to processes for preparing modifiedpigments. In one embodiment, the process comprises the step of:combining, in any order, a pigment having attached an electrophilicgroup and a thiol reagent comprising at least one —SH group and at leasttwo ionic or ionizable groups. Preferably the thiol reagent is analkylthiol substituted with at least two carboxylic acid groups. In asecond embodiment, the process comprises the step of: combining, in anyorder, a pigment having attached an electrophilic group and athiopolymer comprising at least one —SH group and at least one ionic orionizable group. Preferably the thiopolymer comprises the reactionproduct of a polymer having at least one anhydride, at least oneactivated carboxylic acid, or at least one carboxylic acid or saltthereof; an aminoalkane thiol or an aromatic amino thiol; and optionallyan activating agent.

[0010] The present invention further relates to modified pigments. Inone embodiment, the modified pigment comprises a pigment having attacheda group comprising the formula —S—[PI]. In a second embodiment, themodified pigment comprises a pigment having attached a group comprisingthe formula X-Sp-S—[PI], wherein X is an arylene, heteroarylene, oralkylene group, Sp is a spacer group. For both embodiments, PIrepresents an organic group substituted with at least two ionic orionizable groups or a polymeric group comprising at least one ionic orionizable group.

[0011] The present invention further relates to ink compositions, inparticular inkjet ink compositions, comprising the modified pigmentsdescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a graph showing the effect of the targeted percent ofanhydrides reacted with aminoethane thiol (AET) on the expected acidnumber of the resulting product for several styrene-maleic anhydridepolymers.

[0013]FIG. 2 is a graph showing the effect of the targeted percent ofanhydrides reacted with aminoethane thiol (AET) on the expectedmolecular weight of the resulting product for several styrene-maleicanhydride polymers.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention relates to processes for preparing modifiedpigment products as well as to the modified pigment products themselves.

[0015] In the process of the present invention, a pigment havingattached an electrophilic group is combined with an SH-containingcompound. The pigment can be any type of pigment conventionally used bythose skilled in the art, such as black pigments and other coloredpigments. Preferably, when the pigment is a black pigment, the pigmentis carbon black. Mixtures of different pigments can also be used. Thesepigments can also be used in combination with a variety of differenttypes of dispersants in order to form stable dispersions and inks.

[0016] Representative examples of black pigments include various carbonblacks (Pigment Black 7) such as channel blacks, furnace blacks and lampblacks, and include, for example, carbon blacks sold under the Regal®,Black Pearls®, Elftex®, Monarch®, Mogul®, and Vulcan® trademarksavailable from Cabot Corporation (such as Black Pearls® 2000, BlackPearls® 1400, Black Pearls® 1300, Black Pearls® 1100, Black Pearls®1000, Black Pearls®900, Black Pearls®880, Black Pearls® 800, BlackPearls® 700, Black Pearls® L, Elftex® 8, Monarch® 1400, Monarch® 1300,Monarch® 1100, Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800,Monarch® 700, Mogul® L, Regal® 330, Regal® 400, Vulcan® P).

[0017] The pigment may also be chosen from a wide range of conventionalcolored pigments. The colored pigment can be blue, brown, cyan, green,white, violet, magenta, red, orange, yellow, as well as mixturesthereof. Suitable classes of colored pigments include, for example,anthraquinones, phthalocyanine blues, phthalocyanine greens, diazos,monoazos, pyranthrones, perylenes, heterocyclic yellows, quinacridones,and (thio)indigoids. Such pigments are commercially available in eitherpowder or press cake form from a number of sources including, BASFCorporation, Engelhard Corporation and Sun Chemical Corporation.Examples of other suitable colored pigments are described in the ColourIndex, 3rd edition (The Society of Dyers and Colourists, 1982).

[0018] The pigment can have a wide range of BET surface areas, asmeasured by nitrogen adsorption. It is well recognized by those skilledin the art that the pigment may be subject to conventional sizereduction or comminution techniques, such as ball or jet milling, toreduce the pigment to a smaller particle size, if desired.

[0019] The electrophilic group of the pigment used in the process of thepresent invention comprises any group capable of reacting with amaterial having at least one thiol group. Thus, for example, theelectrophilic group may comprise a carboxylic acid or ester, anactivated carboxylic acid, an acid chloride, a sulfonyl chloride, anacyl azide, an isocyanate, a ketone, an aldehyde, an anhydride, anα,β-unsaturated ketone, aldehyde, or sulfone, an alkyl halide, anepoxide, an alkyl sulfonate or sulfate, a triazene, or salts andderivatives thereof. Preferably, the electrophilic group is anα,β-unsaturated ketone, aldehyde, or sulfone group or an alkylsulfategroup or salt thereof. For example, the electrophilic group may be a2-(sulfatoethyl) sulfone group or a salt thereof.

[0020] The pigment having attached an electrophilic group can beprepared using methods known to those skilled in the art. For example,these pigments can be prepared using the methods described in U.S. Pat.Nos. 5,851,280, 5,698,016, 5,922,118, and 5,837,045, and PCT PublicationNos. WO 99/51690 and WO 00/22051, the descriptions of which are fullyincorporated herein by reference. These methods provide for a morestable attachment of the groups onto the pigment compared to traditionaladsorbed groups, such as polymers, surfactants, and the like. Thepigment having attached an electrophilic group may also be preparedusing the method described in PCT Publication No. WO 01/51566, which isincorporated in its entirety herein by reference.

[0021] The amount of electrophilic groups can be varied. Preferably, thetotal amount of electrophilic groups is from about 0.01 to about 10.0micromoles of groups/m² surface area of pigment, as measured by nitrogenadsorption (BET method). For example, the amount of electrophilic groupsis from about 0.5 to about 4.0 micromoles/m². Additional attachedorganic groups which are not reactive with the thiol reagent may also beused.

[0022] The pigment having attached an electrophilic group may bepurified by washing, such as by filtration, centrifugation, or acombination of the two methods, to remove unreacted raw materials,byproduct salts and other reaction impurities. The pigments may also beisolated, for example, by evaporation or it may be recovered byfiltration and drying using known techniques to those skilled in theart. The pigment may also be dispersed into a liquid medium, and theresulting dispersions may be purified or classified to remove impuritiesand other undesirable free species which can co-exist in the dispersionas a result of the manufacturing process. For example, the dispersioncan be purified to remove any undesired free species, such as unreactedtreating agent using known techniques such asultrafiltration/diafiltration, reverse osmosis, or ion exchange.

[0023] In one embodiment, the process of the present invention comprisesthe step of combining a pigment having attached an electrophilic groupand a thiol reagent. In this first embodiment, the thiol reagentcomprises at least one —SH group and at least two ionic or ionizablegroups. As used herein, “at least one” and “at least two” refers to thestoichimetric amount of each group. Thus, for this first embodiment, thethiol reagent has two ionic or ionizable groups for each —SH group. Thethiol reagent can be either an alkyl or aryl thiol that is substitutedwith at least two ionic or ionizable groups. The amount of thiol reagentcan be any amount capable of reacting with the electrophilic groups onthe pigment. Preferably, the ratio of the weight of the thiol reagent tothe weight of the pigment is from about 0.1/1 to about 10/1 and morepreferably from about 0.2/1 to about 2/1.

[0024] An ionic group is either anionic or cationic and is associatedwith a counterion of the opposite charge including inorganic or organiccounterions such as Na⁺, K⁺, Li⁺, NH₄ ⁺, NR′₄ ⁺, acetate, NO₃ ⁻, SO₄ ⁻²,R′SO₃ ⁻, R′OSO₃ ⁻, OH⁻, and Cl⁻, where R′ represents hydrogen or anorganic group such as a substituted or unsubstituted aryl and/or alkylgroup. An ionizable group is one that is capable of forming an ionicgroup in the medium of use. Organic ionic groups include those describedin U.S. Pat. No. 5,698,016, the description of which is fullyincorporated herein by reference.

[0025] The thiol reagent may comprise at least two anionic ofanionizable groups. Anionic groups are negatively charged ionic groupsthat may be generated from groups having ionizable substituents that canform anions (anionizable groups), such as acidic substituents. They mayalso be the anion in the salts of ionizable substituents.

[0026] Representative examples of anionic groups include —COO⁻, —SO₃ ⁻,—OSO₃ ⁻, —HPO₃ ⁻, —OPO₃ ⁻², and —PO₃ ⁻². Representative examples ofanionizable groups include —COOH, —SO₃H, —PO₃H₂, —R′SH, —R′OH, and—SO₂NHCOR′, where R′ represents hydrogen or an organic group such as asubstituted or unsubstituted aryl and/or alkyl group. Preferably, theanionic or anionizable group is a carboxylic acid group, a sulfonic acidgroup, or salts thereof. Thus, the thiol reagent can be an alkylthiolthat is substituted with at least two carboxylic acid groups, such as,for example, mercaptosuccinic acid.

[0027] The thiol reagent may comprise at least one cationic orcationizable group. Cationic groups are positively charged organic ionicgroups that may be generated from ionizable substituents that can formcations (cationizable groups), such as protonated amines. For example,alkyl or aryl amines may be protonated in acidic media to form ammoniumgroups —NR′₂H⁺, where R′ represent an organic group such as asubstituted or unsubstituted aryl and/or alkyl group. The thiol reagentmay also comprise both an anionic or anionizable group and a cationic orcationizable group.

[0028] For this first embodiment, it is preferred that the pigmenthaving attached an electrophilic group and the thiol reagent arecombined under conditions which form the thiolate of the thiol reagent.For example, it is preferred that the pigment and thiol reagent arecombined under alkaline conditions, which form the thiolate and mayassist in the reaction of the thiol reagent with the pigment. Inaddition, alkaline conditions may increase the solubility of the thiolreagent, particularly when the ionic or ionizable groups of the thiolreagent are anionic or anionizable groups. Thus, it is preferred thatthe pigment and thiol reagent are combined at a pH greater than or equalto 7, more preferably greater than or equal to 9, and most preferablygreater than or equal to 11.

[0029] In a second embodiment, the present invention comprises the stepof combining, in any order, a pigment having attached an electrophilicgroup and a thiopolymer comprising at least one —SH group. The —SH groupmay be present along the backbone of the thiopolymer, such as, forexample, as part of a pendant group, or as a terminating group on theend(s) of the polymer. The thiopolymer preferably further comprises atleast one ionic or ionizable group. The ionic or ionizable groups may beany of those described above. Thus, the thiopolymer may be any polymercomprising at least one —SH group and at least one ionic or ionizablegroup. The amount of thiopolymer can be any amount capable of reactingwith the electrophilic groups on the pigment. Preferably, the ratio ofthe weight of thiopolymer to the weight of the pigment is from about0.1/1 to about 10/1, and more preferably from about 0.2/1 to about 2/1.

[0030] Preferably, the thiopolymer comprises the reaction product of apolymer having at least one reactive group, such as an anhydride, anactivated carboxylic acid, or a carboxylic acid group or salt thereof,and a substituted alkyl or aryl thiol, such as an aminoalkane thiol oran aromatic amino thiol. Preferably, the substituted alkyl or aryl thiolis aminoethane thiol.

[0031] Examples of polymers having at least one reactive group includeanhydride polymers, such as poly(styrene-maleic anhydride) andcarboxylic acid polymers, such as polyacrylic acid, polymethacrylicacid, and copolymers of acrylic or methacrylic acid, includingpoly(styrene-acrylic acid), poly(styrene-methacrylic acid),poly(ethylene-acrylic acid), or copolymers of acrylic and methacrylicacid with alkyl acrylates or methacrylates. Other suitable carboxylicacid polymers include polyesters, polyurethanes, and polyamides, whichhave carboxylic acid end groups. If needed to improve the reactivity ofthe carboxylic acid groups, an activating agent may optionally be added,thus forming a polymer having at least one activated carboxylic acid.The activated carboxylic acid may be a mixed anhydride, such as thatformed by the reaction of a carboxylic acid or salt with ethylchloroformate. Other activated carboxylic acid groups and activatingagents to prepare them will be known to one skilled in the art.

[0032] When the thiopolymer is the reaction product of a polymer havingat least one reactive group and a substituted alkyl or aryl thiol, theamount of each reagent need not be stoichiometric. For example, theamount of aminoalkyl or aromatic amino thiol may be less than the amountof the reactive group in the polymer. Any remaining reactive groups maybe further reacted. For example, when the resulting thiopolymer hasremaining anhydride groups, these may be further reacted with base, tohydrolyze the remaining anhydrides and form carboxylic acid groups, orsalts thereof. Alternatively, reagents such as alkyl or aryl amines andalcohols may be added to react with the remaining anhydride groups toform amic acids (or imides) and half acid esters, respectively. Thisresulting thiopolymer can then be used in the process of the presentinvention to be combined with a pigment having attached an electrophilicgroup.

[0033] For this second embodiment, the process of the present inventionmay further comprise the step of adding an alkylating agent. Thealkylating agent is used to “cap” any thiol groups which remain afterthe thiopolymer and pigment having attached an electrophilic group havebeen combined. Alkylating agents for thiol groups are known to oneskilled in the art and include, for example, alkyl halides, haloacetatesor salts thereof, or α,β-unsaturated carbonyl and sulfonyl compoundssuch as acrylates and methacrylates (including, for example, acrylicacid, methacrylic acid, or salts thereof), vinyl sulfonic acid or saltsthereof, and maleates (including, for example, maleic acid or saltsthereof, or maleimide).

[0034] The present invention further relates to a modified pigment. Inone embodiment, the modified pigment comprises a pigment having attacheda group comprising the formula —S—[PI]. The group PI represents anorganic group substituted with at least two ionic or ionizable groups.The pigment and ionic or ionizable groups may be any of those describedabove. For example, the group PI can represent an organic groupcomprising a branched or unbranched alkyl group substituted with atleast two ionic or ionizable groups, preferably at least two carboxylicacid groups. An example of a preferred group PI is a succinic acid groupor salt thereof.

[0035] The group PI may also represent a polymeric group comprising atleast one ionic or ionizable group. The ionic or ionizable groups may beany of those described above. The polymeric group can be a homopolymer,copolymer, terpolymer, and/or a polymer containing any number ofdifferent repeating units. Further, the polymeric group can be a randompolymer, alternating polymer, graft polymer, block polymer, star-likepolymer, and/or comb-like polymer. Preferably, the polymeric groupcomprises a homopolymer or copolymer of acrylic acid, methacrylic acid,maleic acid, or salts thereof.

[0036] In a second embodiment, the modified pigment of the presentinvention comprises a pigment having attached a group comprising theformula —X-Sp-S—[PI]. X, which is directly attached to the pigment,represents an arylene or heteroarylene group or an alkylene group and issubstituted with an Sp group. Sp represents a spacer group. The group PIis as described above and can represent an organic group substitutedwith at least two ionic or ionizable groups or a polymeric groupcomprising at least one ionic or ionizable group.

[0037] The group Sp represents a spacer group which, as used herein, isa link between two groups. The group Sp can be a bond or a chemicalgroup. Examples of chemical groups include, but are not limited to,—O₂C—, —CO—, —COCH₂—, —COC₂H₄—, —OCOCH₂—, —OCOC₂H₄—, —NRCOCH₂—,—NRCOC₂H₄—, —OSO₂—, —SO₂—, —SO₂C₂H₄—, —SOC₂H₄—, —NRSO₂C₂H₄—, —S_(k)—,—NRCO—, —NRCOCH(CH₂CO₂R)—, —NRCOCH₂CH(CO₂R)—, —N(COR)(CO)—, imide groups(including maleimide groups), arylene groups, linear or branchedalkylene groups, and the like. R, which can be the same or different,represents hydrogen or an organic group such as a substituted orunsubstituted aryl or alkyl group, and k is an integer, such as from 1to 7.

[0038] The group X represents an arylene or heteroarylene group or analkylene group. X is directly attached to the pigment and is furthersubstituted with an Sp group. The aromatic group can be furthersubstituted with any group, such as one or more alkyl groups or arylgroups. Preferably, the arylene group is phenylene, naphthylene, orbiphenylene. When X represents an alkylene group, examples include, butare not limited to, substituted or unsubstituted alkylene groups whichmay be branched or unbranched. The alkylene group can be substitutedwith one or more groups, such as aromatic groups. Examples include, butare not limited to, C₁-C₁₂ groups like methylene, ethylene, propylene,or butylene, groups. Preferably, X is an arylene group.

[0039] The group X may be substituted with one or more functionalgroups. Examples of functional groups include, but are not limited to,R″, OR″, COR″, COOR″, OCOR″, carboxylates, halogens, CN, NR″₂, SO₃H,sulfonates, sulfates, NR″(COR″), CONR″₂, NO₂, PO₃H₂, phosphonates,phosphates, N═NR″, SOR″, NSO₂R″, wherein R″ which can be the same ordifferent, is independently hydrogen, branched or unbranched C₁-C₂₀substituted or unsubstituted, saturated or unsaturated hydrocarbons,e.g., alkyl, alkenyl, alkynyl, substituted or unsubstituted aryl,substituted or unsubstituted heteroaryl, substituted or unsubstitutedalkaryl, or substituted or unsubstituted aralkyl.

[0040] As shown by the structure above, the group PI is attached to thepigment through the spacer group Sp and a sulfur atom. However, it willalso be recognized that, when the group PI is a polymeric group, thegroup PI can also be attached to the pigment at multiple points alongthe polymer chain through proper choice of substituent groups on therepeating monomer units. These substituents may also comprise spacergroups or —X-Sp- groups as described above. Thus, these groups can beattached to the pigment at either end or at points along the backbone.

[0041] For the modified pigments of the present invention, the amount ofattached groups can be varied. Preferably, the total amount of attachedgroups is from about 0.01 to about 10.0 micromoles of organic group/m²surface area of pigment, as measured by nitrogen adsorption (BETmethod). For example, the amount of attached groups is between fromabout 0.5 to about 4.0 micromoles/m². Additional attached groups, nothaving the formulas described above, may also be used. Furthermore, themodified pigments of the present invention may be purified using thetechniques and methods described above.

[0042] The modified pigments of the present invention can be used in avariety of applications. For example, the modified pigments can bedispersed in a liquid vehicle and used in an ink or coating application.The vehicle can be either an aqueous or non-aqueous vehicle, dependingon the nature of the attached organic group. In particular, the modifiedpigments can be used in an inkjet ink, such as an aqueous inkjet ink.Suitable additives may be incorporated into these inkjet inkcompositions to impart a number of desired properties while maintainingthe stability of the compositions. For example, surfactants may be addedto further enhance the colloidal stability of the composition. Otheradditives are well known in the art and include humectants, biocides,binders, drying accelerators, penetrants, dyes, buffers, and the like.

[0043] The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature.

EXAMPLES

[0044] For the following examples, the styrene-co-maleic acid polymerswere obtained from the Sartomer Company and are shown in Table 1: TABLE1 Polymer ID M_(W) Styrene:Maleic Anhydride Ratio SMA(1000) 5,500 1:1SMA(2000) 7,250 2:1 SMA(3000) 9,500 3:1 SMA(1440) * 7,500 1.5:1  

[0045] Dimethylformamide (DMF), acrylic acid, mercaptosuccinic acid(MEA), aminoethanethiol hydrochloride (AET HCl),5,5′-dithiobis(2-nitrobenzoioc acid) (DTNB), ethylchloroformate,concentrated HCl, and triethylamine (TEA) were obtained from AldrichChemical Co. and used without further purification. Joncryl® 680 wasobtained from S. C. Johnson.

[0046] Particle size was determined using a Microtrac® Particle SizeAnalyzer, and the values reported are the mean volume particle size(mV). Percent attached polymer was calculated from thermogravimentricanalysis (TGA) using a TA Instruments TGA Model 2950. The samples wereanalyzed under nitrogen according to the following temperature profile:10° C./min up to 110° C., hold at 110° C. for 10 minutes, continueheating at 10° C./min up to 800° C., and hold at 800° C. for 10 minutes.Percent attached material is determined from comparison of the weightlost between 110° C. and 800° C. of the final product compared to thatof the starting materials.

Examples 1-3

[0047] The following examples describe the preparation of a modifiedpigment of the present invention according to Scheme 1 below:

Example 1

[0048] A 14.9% aqueous dispersion of Black Pearls® 880 carbon black(available from Cabot Corporation, Boston, Mass.) having attached a2-(sulfatoethylsulfone) group was prepared according to the proceduredescribed in PCT Publication No. WO 01/51566 to yield a pigmentdispersion. The resulting pigment having attached an electrophilic groupwas analyzed for sodium content to determine that the amount of attachedgroup was 0.3 mmol/g of dry carbon black.

[0049] A solution of 0.5 g (3.33 mmol) mercaptosuccinic acid in 5 ml ofdeionized water was mixed with 20 g of the above pigment dispersion in around bottom flask and the resultant mixture was stirred at roomtemperature, under an atmosphere of nitrogen. To this was added dropwise15 ml of 1N NaOH to afford a pH of 12.8 and then the mixture was stirredovernight to give a dispersion of a modified pigment.

[0050] The modified pigment dispersion was purified by diafiltrationusing a polysulfone hollow fiber membrane with a pore size of 0.05microns. The solution was first concentrated to 35 ml and thendiafiltered with 175 ml 0.1M NaOH followed by 245 ml of deionized water.The final pH of the permeate was between 6-7.

[0051] The resulting purified modified pigment dispersion had a particlesize of 112 nm and a pH of 11.0. The modified carbon black pigment wasanalyzed for sodium and compared to the starting pigment having attachedan electrophilic group. Results are shown in Table 2 below.

Example 2

[0052] For this example, the procedure described in Example 1 wasfollowed, with the exception that the dispersion of Black Pearls® 880carbon black having attached a 2-(sulfatoethylsulfone) group wasreplaced with a 5.7% solids dispersion of Pigment Yellow 74 (availablefrom Sun Chemical) having the same attached electrophilic group, alsoprepared according to the procedure described in WO 01/51560. Resultsfrom the Na+ analysis of this modified pigment are shown in Table 2below.

Example 3

[0053] For this example, the procedure described in Example 1 wasfollowed, with the exception that the dispersion of Black Pearls® 880carbon black having attached a 2-(sulfatoethylsulfone) group wasreplaced with a 20.51% solids dispersion of Pigment Red 122 (availablefrom Sun Chemical) having the same attached electrophilic group, alsoprepared according to the procedure described in WO 01/51560. Resultsfrom the Na+ analysis of this modified pigment are shown in Table 2below. TABLE 2 Example % Na % Na # Pigment before after 1 Black Pearls ®880 0.69 1.1 carbon black 2 Pigment Yellow 74 0.20 0.50 3 Pigment Red122 0.50 0.77

Examples 4-11

[0054] The following examples describe the preparation of anaminoethanethiolated-SMA (styrene-maleic anhydride) polymer andsubsequent modified pigment according to Scheme 2 below:

[0055] Aminoethanethiol is reacted in DMF with some or all of theanhydrides of the SMA polymer. The resulting product molecular weightand acid number have a direct correlation to the extent of thisreaction. FIG. 1 and FIG. 2 show the expected dependence of molecularweight and acid number on the targeted percentage of anhydrides reactedwith aminoethane thiol. These are determined from the theoretical ratioof styrene/maleic anhydride in the starting polymer. For example,SMA(3000) has a 3/1 ratio of styrene to maleic anhydride (from themanufacturer's product sheet). If 50% of the anhydride groups aretargeted for reaction with AET.HCl, the expected acid number for theresulting product would be approximately 190 and the expected MW wouldbe approximately 10400. Thus, by targeting the percent of anhydridesreacted with the thiol reagent, the properties of the polymer and thesubsequent modified pigment may be controlled.

Example 4

[0056] A solution was prepared by dissolving 20 g (0.049 mol anhydride)of SMA(3000) in 100 ml of dry DMF. To this stirred solution, at roomtemperature, under a steady stream of nitrogen gas, was added 4.2 g(0.037 mol) of 2-aminoethanethiol hydrochloride as a solid in oneportion and then 5.2 ml (0.074 mol) triethylamine, dropwise. Theresultant mixture was heated at 45° C. for 30 minutes and then at roomtemperature for 4.5 hours. The product was isolated by slowly droppinginto vigorously stirred 1N HCl (600 ml). After the addition, the mixturewas stirred for another 60 minutes and then suction filtered, washedwith 400 ml of 1N HCl and then 400 ML of deionized water. The resultingproduct was briefly air dried to afford 61 g of a free flowing whitesolid which contained 62% moisture, as measured by weight loss afterheating at 110° C. for 1 hour.

[0057] The aminoethanethiolated-SMA polymer was dried at 110° C. Resultsfrom elemental combustion analysis are shown in Table 3 below. Thiolswere measured by titration with DTNB following a modification ofEllman's procedure (Ellman, G. L. (1958) Arch. Biochem. Biophys. 74,443; Bioconjugate Techniques, Greg T. Hermanson, Academic Press, Inc.,copyright 1996, p 88). The resulting polymer was found to have 1.4 mmolthiols/g dry polymer.

Example 5

[0058] For this example, the procedure described for Example 4 was used,with the differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 6

[0059] For this example, the procedure described for Example 4 was used,with the differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 7

[0060] For this example, the procedure described for Example 4 was used,with the differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 8

[0061] For this example, the procedure described for Example 4 was used,with the differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below. Example 9

[0062] For this example, the procedure described for Example 4 was used,with the differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 10

[0063] For this example, the procedure described for Example 4 was used,with the differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below. TABLE 3Ex. Anhydrides AET.HCl % S % S % N % N # Polymer (mol) (mol) (Theor.)*(Actual) (Theor.)* (Actual) 4 SMA(3000) 0.049 0.037 5.14 5.18 2.25 2.485 SMA(3000) 0.049 0.049 6.39 6.66 2.79 2.83 6 SMA(3000) 0.049 0.021 3.123.07 1.36 1.65 7 SMA(2000) 0.065 0.065 8.12 8.46 3.55 3.33 8 SMA(2000)0.065 0.047 6.46 7.21 2.83 3.16 9 SMA(1000) 0.10 0.10 11.5 9.14 5.03 4.410 SMA(1440) 0.11 0.11 2.20 1.55 0.97 0.83

Example 11

[0064] A solution of 145 ml of 1M NaOH was magnetically stirred in around bottom flask at room temperature while nitrogen gas was bubbledthrough the liquid for 10 minutes. To this was added 54.8 g of theaminoethanethiolated polymer of Example 4 (62% moisture content). Theresultant mixture was heated under nitrogen to 40-50° C. until a clearyellow solution was obtained.

[0065] The 14.9%₀ aqueous dispersion of Black Pearls® 880 carbon blackhaving attached a 2-(sulfatoethylsulfone) group described in Example 1(140 g) was added dropwise to the yellow polymer solution overapproximately 5 minutes. An additional 13 ml of 1N NaOH was added toraise the pH to 12-13. The resultant mixture was then stirred at 40-50°C. for 3.5 hours to give a dispersion of the modified pigment of thepresent invention.

[0066] A sodium acrylate solution was prepared by dissolving 7.5 mlacrylic acid into deionized water containing 11.7 g of NaCO₃. Thissolution was added to the modified pigment dispersion to “cap” anyunreacted thiol groups. Heating and stirring were continued for another3 hours and the mixture was then allowed to cool slowly to roomtemperature. The dispersion of the resulting capped modified pigment waspurified by diafiltration as described in Example 1 to reach a finalpermeate polymer concentration of <50 ppm (monitored by measuring theabsorbance of the permeate at 250 nm in a UV-VIS Spectrometer; theconcentration of polymer is calculated from the known epsilon).

[0067] The capped modified pigment dispersion (11.6% solids, pH=10.15)was found to have a particle size of 120.4 nm and a sodium level of 1.3%(based on the dried carbon black solid). TGA analysis showed that theattached polymer accounted for 14% of the total weight.

Examples 12-13

[0068] The following examples describe the preparation of anaminothiolated-SAA (styrene-acrylic acid) polymer and subsequentmodified pigment according to

[0069] Scheme 3 below:

Example 12

[0070] To a magnetically stirred solution of 10 g styrene-co-acrylicacid, (Joncryl® 680: M_(w)=4,900, Acid Number=215) dissolved in 100 mlDMF under a steady stream of nitrogen at room temperature was added 5.4ml (0.039 mol) of triethylamine. To this was added 1.84 ml (0.019 mol)of ethylchloroformate. The solution became slightly warm with some gasevolution and cloudiness. The resultant mixture was stirred at roomtemperature for 40 minutes. A solution of 2.2 g (0.019 mol)aminoethanethiol hydrochloride and 2.7 ml (0.019 mol) triethylamine in50 ml DMF was added dropwise to this mixture over 15 minutes, and theresulting cloudy solution was stirred overnight. The product wasprecipitated by slowly dropping into a rapidly stirred solution of 1NHCl (250 ml). The resulting white precipitate was suction filtered,washed with cold 1N HCl, cold deionized water, and then air dried toafford a chalky white solid. A sample of this aminoethanethiolated SAApolymer was dried at 110° C. Elemental combustion analysis results wereas follows: 71.84% C; 7.53% H; 1.53% N; 3.01% S.

Example 13

[0071] A solution of 12.5 ml of 0.5 M NaOH was magnetically stirred atroom temperature while nitrogen gas was bubbled through the liquid for10 minutes. To this was added 1 g of the aminoethanethiolated SAApolymer of Example 12. To the resulting solution was added 2.9 g of the14.9% aqueous dispersion of Black Pearls® 880 carbon black havingattached a 2-(sulfatoethylsulfone) group described in Example 1. Thisgave a final pH of 12.5. This solution was stirred under nitrogen gasovernight. The resulting modified pigment was purified by diafiltrationas described in Example 1 to give a dispersion having the followingphysical properties: pigment concentration: 9.0% (wt/wt); UPA mv=137 nm;% N=0.48%; % S=2.28%; %sulfate=0.35%. TGA analysis showed that theattached polymer accounted for 6% of the total weight.

Examples 14-15

[0072] The following examples describe the preparation of anaminoethanethiolated-SMA (styrene-maleic anhydride) polymer additionallyfunctionalized with an alkylamine. In Example 14 the alkylamine isaminoethane sulfonic acid and in Example 15 the alkylamine is apolyamine (Jeffamine® XTJ506).

Example 14

[0073] To a 3-neck round bottom flask equipped with an overhead stirrerwas added 1.5 liters of DMF followed by 300 g (0.735 mol anhydride) ofSMA(3000). The polymer suspension was heated to 40-50° C. to produce apolymer solution. The polymer solution was then de-oxygenated usingnitrogen. To this heated polymer solution under nitrogen was added 33.2g of aminoethanethiol hydrochloride (0.29 mol) and 45.9 g of aminoethanesulfonic acid (0.367 mol), and the mixture was stirred for an additional30 minutes at 40-50° C. Then 133 g of triethylamine (1.32 mol) was addeddropwise. The mixture was allowed to stir, coming to room temperature,overnight. The solution was then added dropwise into 7 liters of 1 MHCl. The resulting white solid was filtered, washed three times with 1liter of 1 M HCl and four times with 2 liters of DI-water, and thenair-dried. Elemental analyses showed that the product contained 2.13%nitrogen and 5.57% sulfur (theoretical values are 2.5% nitrogen and 6%sulfur).

Example 15

[0074] To a 3-neck round bottom flask equipped with an overhead stirrerwas added 1.5 liters of DMF followed by 300 g (0.735 mol anhydride) ofSMA(3000). The polymer suspension was heated to 40-50° C. to produce apolymer solution. The polymer solution was then de-oxygenated usingnitrogen. To this heated polymer solution under nitrogen was added 41.5g of aminoethanethiol hydrochloride (0.355 mol) and 146 g of Jeffamine®XTJ506 (0.146 mol, available from Huntsman Corporation), and the mixturewas stirred for an additional 30 minutes at 40-50° C. Then 96 g oftriethylamine (0.95 mol) was added dropwise. The mixture was allowed tostir overnight at room temperature under a nitrogen blanket. Thesolution was then added dropwise into 7 liters of 1 M HCl. The resultingwhite solid was filtered, washed three times with 1 liter of 1 M HCl andfour times with 2 liters of DI-water, and then air-dried. Elementalanalyses showed that the product contained 1.21% nitrogen and 2.38%sulfur (theoretical values are 1.1% nitrogen and 2.48% sulfur).

Example 16

[0075] A solution of 100 mL of NaOH was magnetically stirred in a roundbottom flask at room temperature while nitrogen gas was bubbled throughthe liquid for 10 minutes. To this was added 37 g of the SMA polymer ofExample 14 (46% moisture content). The resultant mixture was heatedunder nitrogen to 40-50° C. until a clear yellow solution was obtained.

[0076] A 10% aqueous dispersion of Black Pearls® 1100 carbon blackhaving attached a 2-(sulfatoethylsulfone) group (400 g), preparedaccording to the procedure described in WO 01/51560, was added dropwiseto the yellow polymer solution over 10 minutes. An additional 25 mL of 1M NaOH was added to raise the pH to 12-13. The reaction mixture was thenstirred at room temperature overnight to give a dispersion of themodified pigment of the present invention.

[0077] To the dispersion was added 6.55 g of sodium acrylate to “cap”any unreacted thiol groups. The mixture was allowed to stir for another2 hours at room temperature. The dispersion of the resulting cappedmodified pigment was purified by diafiltration as described in Example 1to reach a final permeate polymer concentration of <50 ppm (monitored bymeasuring the absorbance of the permeate at 250 nm in a UV-VISSpectrometer; the concentration of polymer is calculated from the knownepsilon).

[0078] The capped modified pigment dispersion (9.5% solids, pH 9.72) wasfound to have a mean volume particle size of 108 nm and a sodium levelof 2.5% (based on the dried carbon black solid). TGA analysis showedthat the attached polymer accounted for 16% of the total solid weight.

Example 17

[0079] A solution of 280 mL of NaOH was magnetically stirred in a roundbottom flask at room temperature while nitrogen gas was bubbled throughthe liquid for 10 minutes. To this was added 322 g of the SMA polymer ofExample 15 (69% moisture content). The resultant mixture was heatedunder nitrogen to 40-50° C. until a clear yellow solution was obtained.

[0080] The 10% aqueous dispersion of Black Pearls® 1100 carbon blackhaving attached a 2-(sulfatoethylsulfone) group (1000 g) used in Example16 was added dropwise to the yellow polymer solution over 10 minutes. Anadditional 60 mL of 1 M NaOH was added to raise the pH to 12-13. Thereaction mixture was then stirred at room temperature overnight to givea dispersion of the modified pigment of the present invention.

[0081] To the dispersion was added 14 g of sodium acrylate to “cap” anyunreacted thiol groups. The mixture was allowed to stir for another 2hours at room temperature. The dispersion of the resulting cappedmodified pigment was purified by diafiltration as described in Example 1to reach a final permeate polymer concentration of <50 ppm (monitored bymeasuring the absorbance of the permeate at 250 nm in a UV-VISSpectrometer; the concentration of polymer is calculated from the knownepsilon).

[0082] The capped modified pigment dispersion (10.4% solids, pH=9.51)was found to have a mean volume particle size of 78 nm and a sodiumlevel of 1.3% (based on the dried carbon black solid). TGA analysisshowed that the attached polymer accounted for 24% of the total solidweight.

What we claim is:
 1. A process for preparing a modified pigmentcomprising the step of: combining, in any order, a pigment havingattached an electrophilic group and a thiol reagent comprising at leastone —SH group and at least two ionic or ionizable groups.
 2. The processof claim 1, wherein the pigment having attached an electrophilic groupcomprises the reaction product of a pigment and a diazonium saltcomprising the electrophilic group.
 3. The process of claim 1, whereinthe pigment comprises a blue pigment, a black pigment, a brown pigment,a cyan pigment, a green pigment, a white pigment, a violet pigment, amagenta pigment, a red pigment, an orange pigment, a yellow pigment, ormixtures thereof.
 4. The process of claim 1, wherein the pigment iscarbon black.
 5. The process of claim 1, wherein the electrophilic groupcomprises an alkylsulfate group or salt thereof or an α,β-unsaturatedketone, aldehyde, or sulfone.
 6. The process of claim 1, wherein theelectrophilic group comprises a 2-(sulfatoethyl) sulfone group or saltthereof.
 7. The process of claim 1, wherein at least one of the ionic orionizable groups is a carboxylic acid group, a sulfonic acid group, or asalt thereof.
 8. The process of claim 1, wherein the thiol reagent is analkylthiol substituted with at least two carboxylic acid groups.
 9. Theprocess of claim 8, wherein the thiol reagent is mercaptosuccinic acid.10. A process for preparing a modified pigment comprising the step of:combining, in any order, a pigment having attached an electrophilicgroup and a thiopolymer comprising at least one —SH group and at leastone ionic or ionizable group.
 11. The process of claim 10, wherein thethiopolymer comprises the reaction product of a polymer having at leastone anhydride, at least one activated carboxylic acid, or at least onecarboxylic acid or salt thereof, an aminoalkane thiol or an aromaticamino thiol, and optionally an activating agent.
 12. The process ofclaim 11, wherein the aminoalkyl thiol is aminoethane thiol.
 13. Theprocess of claim 10, wherein the —SH group is a terminating group of thethiopolymer.
 14. The process of claim 10, wherein the thiopolymer is ahomopolymer or copolymer of maleic anhydride or acrylic acid,methacrylic acid, maleic acid, or a salt thereof.
 15. The process ofclaim 11, wherein the polymer is selected from the group consisting of:polyacrylic acid, polymethacrylic acid, poly(styrene-acrylic acid),poly(styrene-methacrylic acid), poly(styrene-maleic acid),poly(styrene-maleic anhydride), copolymers of acrylic acid ormethacrylic acid and alkyl acrylates or methacrylates,poly(ethylene-acrylic acid), or salts thereof.
 16. The process of claim10, further comprising the step of adding an alkylating agent.
 17. Theprocess of claim 16, wherein the alkylating agent is an alkyl halide, ahaloacetate, an α,β-unsaturated carbonyl compound, or an α,β-unsaturatedsulfonyl compound.
 18. The process of claim 10, wherein the thiopolymercomprises the reaction product of a polymer having at least oneanhydride, at least one activated carboxylic acid, or at least onecarboxylic acid or salt thereof, an aminoalkane thiol or an aromaticamino thiol, an optional activating agent, and an alkylamine, arylamine,or alcohol.
 19. The process of claim 18, wherein the thiopolymercomprises maleic anhydride.
 20. A modified pigment comprising a pigmenthaving attached a group comprising the formula —S—[PI], wherein PIrepresents an organic group substituted with at least two ionic orionizable groups or wherein PI represents a polymeric group comprisingat least one ionic or ionizable group.
 21. The modified pigment of claim20, wherein the ionic or ionizable group is a carboxylic acid group, asulfonic acid group, or a salt thereof.
 22. The modified pigment ofclaim 20, wherein PI represents an organic group comprising a branchedor unbranched alkyl group substituted with at least two carboxylic acidgroups.
 23. The modified pigment of claim 22, wherein PI is a succinicacid group or salt thereof.
 24. The modified pigment of claim 20,wherein PI represents a polymeric group comprising at least one ionic orionizable group.
 25. The modified pigment of claim 24, wherein the ionicor ionizable group is a carboxylic acid group, a sulfonic acid group, ora salt thereof.
 26. The modified pigment product of claim 24, whereinthe polymeric group comprises a homopolymer or copolymer of acrylicacid, methacrylic acid, maleic acid, or salts thereof.
 27. A modifiedpigment comprising a pigment having attached a group comprising theformula —X-Sp-S—[PI], wherein X is an arylene, heteroarylene, oralkylene group, Sp is a spacer group, and PI represents an organic groupsubstituted with at least two ionic or ionizable groups or wherein PIrepresents a polymeric group comprising at least one ionic or ionizablegroup.
 28. The modified pigment of claim 27, wherein the ionic orionizable group is a carboxylic acid group, a sulfonic acid group, or asalt thereof.
 29. The modified pigment of claim 27, wherein PIrepresents an organic group comprising a branched or unbranched alkylgroup substituted with at least two carboxylic acid groups.
 30. Themodified pigment of claim 29, wherein PI is a succinic acid group orsalt thereof.
 31. The modified pigment of claim 27, wherein PIrepresents a polymeric group comprising at least one ionic or ionizablegroup.
 32. The modified pigment of claim 31, wherein the ionic orionizable group is a carboxylic acid group, a sulfonic acid group, or asalt thereof.
 33. The modified pigment product of claim 31, wherein thepolymeric group comprises a homopolymer or copolymer of acrylic acid,methacrylic acid, maleic acid, or salts thereof.
 34. The modifiedpigment of claim 20, wherein at least two ionic or ionizable groups arepresent.
 35. The modified pigment of claim 27, wherein at least twoionic or ionizable groups are present.
 36. An ink composition comprisinga) a liquid vehicle and b) the modified pigment of claim
 20. 37. The inkcomposition of claim 36, wherein the ink composition is an inkjet inkcomposition.
 38. An ink composition comprising a) a liquid vehicle andb) the modified pigment of claim
 27. 39. The ink composition of claim38, wherein the ink composition is an inkjet ink composition.
 40. An inkcomposition comprising a) a liquid vehicle and b) the modified pigmentof claim 35.